The field of art to which this invention pertains is stable emulsions of water soluble gums.
Various synthetic and natural water soluble polymers have been developed which exhibit superior thickening and flocculating properties in aqueous solutions. These polymers are being used increasingly in a number of commercial applications, such as in the clarification of aqueous systems, in paper making operations, in the treatment of sewage and industrial waste, in stabilizers for drilling muds and in the secondary recovery of petroleum by water flooding and by fracturing.
Although these polymers are available commercially as powders or as finely divided solids, they are most frequently utilized as aqueous solutions. This requires the solid polymeric material to be dissolved in water. This is a time consuming step as well as one which has serious drawbacks with respect to the actual dispersion of the solid material in the aqueous medium. Although the various polymers are more or less soluble in water, difficulty is often experienced in preparing aqueous polymer solutions because of the polymer's slow dissolution and because the solid polymer is not readily dispersible in water. Furthermore, dispersions of solid polymers in water are hindered by the tendency to clump or remain as agglomerates on contact with water. Lumps of solid polymer immediately form by the encapsulation of undissolved solids in an outer coating of water-wet polymer, which retards the penetration of additional water into the agglomerate. Although many of these lumps can be dissolved by continued agitation, it is usually not practical to agitate the solution for a time sufficient to obtain complete dissolution of the polymer.
Various means have been proposed to facilitate the dissolution of water soluble polymers in water. In U.S. Pat. No. 3,122,203, polyacrylamide is intimately mixed with a dispersing agent and a finely divided inert solid carrier and this mixture is then dispersed in an organic liquid. Although aqueous solutions of the polymer can be made by adding the dispersion to water with minimal agitation, the organic dispersions themselves are not stable in that the polymer rather quickly will settle to the bottom of the container with hard caking.
In U.S. Pat. No. 3,503,895, a water soluble gum is blended with a solution of a surfactant in an organic liquid. When thoroughly blended, the solvent is evaporated leaving a dry powder. This dry powder will dissolve more readily than the untreated gum. However, the large amount of surfactant required to render the gum readily soluble is detrimental in some applications.
French Patent No. 1,485,729 discloses dispersions of water soluble gums in water miscible solvents, such as glycerol and ethylene glycol. Such dispersions can be rapidly dissolved in water. However, the dispersions themselves are unstable in that the gums settle out and form hard cakes in the bottom of the container.
U.S. Pat. Nos. 28,474 and 28,576 describe inverse emulsions which are aqueous solutions of water soluble polymers dispersed in organic liquids to form water-in-oil emulsions. Such emulsions can be added to water to rapidly form aqueous solutions of the polymers.
Inverse emulsions can also be made by adding water with agitation to an oil-emulsifier mixture to form an emulsion. Finely divided polymer particles are then added to the emulsion with rapid agitation followed by passing the mixture through a homogenizer.